Formaldehyde is a well-known antimicrobial agent that has been used widely to extend the shelf life of certain preparations that are susceptible to microbial growth. These preparations may include industrial products such as liquid detergents, water-based surfactants, soft soaps, water-based paints, fabric softeners, room deodorizers/air fresheners, polymer emulsions, protective coatings for textiles, architectural coatings, water-based gels, sealants and caulks, latexes for paper coatings, water-based inks, wood preservatives, etc. They may also include personal care products such as cosmetics, shampoos, creams, lotions, powder products, etc.
However, formaldehyde, particularly in high concentrations, has many disadvantages, such as an unpleasant odor, a propensity to irritate skin, and a short shelf life due to its high volatility. More importantly, formaldehyde has come under increasingly greater scrutiny by the medical community and by regulatory agencies due to its potential as a health risk.
DMDMH is a formaldehyde donor which releases formaldehyde slowly over a relatively long period of time and is typically produced by methylolating one mole of DMH with two moles of formaldehyde. MDMH, another formaldehyde donor, is prepared also by the methylolation using one mole of formaldehyde.
Foelsch, U.S. Pat. No. 3,987,184, discloses a method for the production of DMDMH which involves reacting 1.85 to 2.4 moles of formaldehyde per mole of 5,5-DMH in water, at a pH of from about 7 to about 9, for a period of about 20 minutes, at a temperature of about 22.degree. to 65.degree. C. Foelsch hypothesized that DMDMH solutions prepared in this manner would have under 1% by weight of free formaldehyde, but he exemplified only solutions having 1.2% by weight of free formaldehyde.
Alternative methods for achieving low free formaldehyde in DMDMH solutions have included the addition of ammonium carbonate to DMDMH solutions or the vacuum stripping of residual free formaldehyde from DMDMH solutions. These attempts have been unsuccessful in lowering free formaldehyde content below 0.1% by weight, however.